Temperature Sensor Problems

Hello.
Does anyone here have any knowledge about temperature measurement?
(My sample is from a 1.6L engine in a 1999 Cordoba, but it should be similar for all.)
The effect is as follows:
- The overheat lamp illuminates intermittently.
- Temperature reading consistently at 90°
- During diagnosis - Function test: Over-temperature indicator does not illuminate.
- The engine temperature diagnostic indicator is fluctuating between 45°C and 90°C.
(During the diagnosis, the overheat LED was not lit, and the instrument was stuck at 90°C (except during the analog display test).)

Here's the translation:

'The question is: Is only the temperature sensor in the control unit faulty (loose connection), or is the over-temperature signal generation in the dashboard also malfunctioning?'
How is the 'Over-Temperature Test' diagnostic signal generated?
How is the 'Over Temperature' signal generated during operation: locally in the display based on the thermometer signal, or by the engine control unit?

BB Stefan.

Good question, our 1F-Ibiza still has an analog cockpit.

However, it also has a faulty temperature sensor. The sensor for the instrument cluster is completely broken (it only shows a very cold reading). Since the sensor for the engine control unit is working fine, I'm not going to fix it. It wouldn't be expensive, but I'm just too lazy, and the car is already pretty dirty anyway...

'Try using a 2k-ohm potentiometer and slowly rotate it while observing the reported temperatures on the tester.'

I've tried the 'overtemperature' actuator test multiple times unsuccessfully on some vehicles... it seems to be a firmware bug. When triggered manually (using the potentiometer), the warning works perfectly.

CU Gremlin.

Hello,

Does the light also blink when the coolant level is too low? At least, that's how it was in my 2-liter gasoline-powered Cordoba.

Sometimes the coolant reservoir gets dirty. Simply remove the reservoir from the coolant tank and clean it with water and dish soap.

Hmm, if the lamp also indicates the coolant level, I know what the problem was (very associative light ...
The boy is actually pouring cooling water up to a level just 2 cm above the bottom edge of the container, and then maintaining that level.
(No leaks visible from the inside or outside, so I don't think there's anything critical.)

I will check that, thanks for the information!

Stefan.